linux-ext4 - Re: [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow

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Date:   Mon, 30 Mar 2020 15:27:12 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow_tree()

On Mon, Mar 30, 2020 at 11:09:32AM +0200, Jan Kara wrote:
> There is an off-by-one error in dx_grow_tree() when checking whether we
> can add another level to the tree. Thus we can grow tree too much
> leading to possible crashes in the library or corrupted filesystem. Fix
> the bug.

Looks good, thanks

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

Don't we have basically the same off-by-one in
e2fsck/pass1.c handle_htree() ?

       if ((root->indirect_levels > ext2_dir_htree_level(fs)) &&
           fix_problem(ctx, PR_1_HTREE_DEPTH, pctx))

-Lukas

> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  lib/ext2fs/link.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/ext2fs/link.c b/lib/ext2fs/link.c
> index 7b5bb022117c..469eea8cd06d 100644
> --- a/lib/ext2fs/link.c
> +++ b/lib/ext2fs/link.c
> @@ -473,7 +473,7 @@ static errcode_t dx_grow_tree(ext2_filsys fs, ext2_ino_t dir,
>  		    ext2fs_le16_to_cpu(info->frames[i].head->limit))
>  			break;
>  	/* Need to grow tree depth? */
> -	if (i < 0 && info->levels > ext2_dir_htree_level(fs))
> +	if (i < 0 && info->levels >= ext2_dir_htree_level(fs))
>  		return EXT2_ET_DIR_NO_SPACE;
>  	lblk = size / fs->blocksize;
>  	size += fs->blocksize;
> -- 
> 2.16.4
>